As of January 21, 2019, the 2018 Form 8936 has not been released yet. Some other 2018 forms have also not been released; they are only partly done with 2018 tax forms and they release more every day. Note that the tax filing season does not start until January 28.
– user102008Jan 22 at 7:44

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Update: the 2018 Form 8936 form and instructions are now online.
– user102008Jan 29 at 6:26